Properties of (Hg,X)-1223 superconductors synthesized without using a glove box

We tried to synthesize (Hg,X)Ba/sub 2/Ca/sub n-1/Ca/sub n/O/sub y/ (MgX-12(n-1)n) superconductors for the substitution of various elements X without using a glove box. For X=V, Cr, Mn, Ge, Mo, Ru and Re, we succeeded in the formation of the phases of n=2, 1, 2, 1, 3, 3 and 3, respectively. It is suggested that the substitution of X for Hg is effective to stabilize the structures of HgX-12(n-1)n phases. Studies of microstructure and superconducting properties on HgMo- and HgRe-1223 revealed that the melt texturing was observed only for HgMo-1223 and that the T/sub c/´s of both samples were above 130 K, almost equal to that of Hg-1223. The irreversibility fields of HgMo- and HgRe-1223 were roughly estimated to be about 1.6 and 3 T at 90 K, respectively. These values are higher than that of Hg-1223. It is speculated that this enhancement is due to the improved coupling of Cu-O planes by the contraction of c-axis or the carrier doping by oxygen atoms introduced in the Hg-(O) layer.